The Nature of Intelligence
and Intelligent Systems
Throughout most of the history of psychology, concepts of general intelligence have been derived primarily from the methods and results of psychometric techniques. In recent decades, the possibility of a science of intelligence, as distinguished from an applied technology of intelligence testing, has been derived from computational theories of cognitive processes. The most influential of these computational theories with respect to theoretical coherence and empirical results is the physical-symbol system hypothesis formulated by Newell and Simon ( 1976).
The mathematical and philosophical background for the physical-symbol system hypothesis of Newell and Simon is the seminal work of Alan Turing ( 1936, 1950). Turing, in a self-scrutiny of his mathematical work, found that his cognitive processes could be reduced to the discovery and application of effective procedures ( Turing, 1936), that is of rigorous syntactic operations on symbol structures. In computing machinery and intelligence, Turing ( 1950) presented his thesis that effective procedures were the necessary and sufficient conditions for intelligence in general. Turing's theoretical unification of computer and intelligence and of brain and computer and its abstract mathematical representation in a universal Turing machine is the intellectual forebear of the physical symbol system hypothesis: